Valve Vault Infiltration Grouting

The Job

This valve vault infiltration grouting project is part of the Purple Line project in Maryland. A large diameter water line was relocated, with the tie-in done inside a 10′ diameter vault that was about 20′ deep. The vault structure, which is precast, and set inside a line plate shaft, was leaking at multiple joints and at a poured in place pipe penetration closure.

The Challenge

The vault structure wasn’t concentric in the shaft. This left little room to pour the closure around the pipe penetrations. One of the penetrations leaked, causing the structure to completely fill with water. Per specifications, it needed to be dry.

Most of the shaft was backfilled with 57 stone. Highly permeable backfill material can make water control grouting particularly difficult. When grouting to seal relatively tight leaks in a structure, the less permeable the adjacent soils the better. All grouts want to take the path of least resistance, and with highly permeable backfills, that often means traveling out into, and permeating, the backfill material instead of into tight cracks and water passageways.

The Solution

CJGeo proposed grouting the infiltration points with CJGrout-35NHV61. 35NHV61 is a hydroinsensitive, plural component geotechnical polyurethane, certified for potable water contact. 35NHV61 is a moderately mobile grout, selected to minimize mobility into the 57 stone backfill and reduce material loss during grouting.

CJGeo mobilized a three person crew to the site, and performed the valve vault infiltration grouting over a few hours.